The issue is rather that nothing in your rule-of-thumb works.
Frozen corn vs whole corn? Were you planning to eat the cob? Does it help my diet to cut corn kernels off manually? How?
Meat you have to cut? Maybe you're thinking hot dogs here, my first thought was ground beef. Does breaking out the meat grinder, and cleaning it, help me eat right? How?
Fish you have to filet? Can I just buy the filets? Or is it 100% necessary that fish skin rot in my garbage can.
Boxed wine? Generally I consider corked wine undrinkable, and I struggle to think what other contribution a cork per se can offer to wine.
Sliced bread? I mean. Look it's a really bad set of rules so I'll have mercy here, the kind of bread which is available only sliced is not great for you, so at least here I can infer your meaning.
Not that it matters because the #1 source of extra pounds on my waist is whole loaves of sourdough bread. I slice them myself.